Since their inception in 1993 OFSTED inspections have generated considerable controversy amongst teachers and educationists generally, Much of the criticism to date has centred on the effects which such inspections have had on schools and their staffs. In contrast little sustained concern has been shown about the underlying assumptions of the OFSTED inspection process. This article identifies as the central feature of that process a particular but tacit conception of judgement. This conception is examined from an essentially Wittgensteinian perspective and (...) is shown to rely on an imprecise understanding of the nature of criteria. It is argued that the OFSTED approach implicitly represents what are in fact conventional criteria, having no guarantee of broad agreement, as if they were criteria having such agreement. As a result severe doubts are raised about the validity of the judgements made and hence of the inspection process generally. (shrink)